Microbiologically safe drinking water is recognized as an essential need by federal and state regulatory agencies, world public health organizations and the lay public. The benefit, to developed (industrialized) and developing nations alike, of a more effective, affordable, broadly applicable and easily applied water treatment disinfection technology cannot be overemphasized.
The World Health Organization (WHO) estimates that approximately 20% of the world's population, or 1.7 billion people, lack access to improved and safe water supplies and that three to four million people, mostly children, die annually from illnesses associated with unsafe drinking water. In the United States, the U.S. Centers for Disease Control and Prevention (CDC) estimates that, including reported and unreported outbreaks, 940,000 cases of illness and potentially 900 deaths occur annually from waterborne microbial infection. Subsets of the general population, including infants, the elderly, organ transplant patients, cancer therapy patients, AIDS patients and other persons with compromised immune systems are at increased risk of waterborne disease.
The U.S. Environmental Protection Agency (EPA) specifies and regulates drinking water quality in the United States for over 170,000 public water systems (PWSs). Of these, over 160,000 PWSs are classified as “small” or “very small” meaning that they serve between 25 and 3,300 people. The present invention may be used as a disinfectant for PWSs. This is significant as EPA has recognized the many drawbacks to chlorine, the most commonly used disinfectant for PWSs. The EPA has expressed interest in and has funded research regarding innovative alternative water treatment technologies. The most significant drawbacks to the use of chlorine as a disinfectant is the formation of disinfection by-products (DBPs), some of which are toxic and suspected carcinogens. This limits the use of chlorine and/or mandates additional treatment to reduce DBP formation. In addition, chlorine's effectiveness can be limited by the physical and/or chemical characteristics of the water sought to be purified. Such limiting factors of chlorine's purification effectiveness include the water's temperature, pH, presence of organic carbon, dissolved organic and inorganic matter, and turbidity. The use of chlorine as a disinfectant also has aesthetic taste and odor concerns as well as safety issues associated with handling the chlorine.
Many of the alternative technologies currently recognized by the EPA in its Alternative Disinfectants and Oxidants Guidance Manual have limitations for widespread use for drinking water disinfection. In addition, many of the alternatives still result in DBP and/or inorganic byproduct formation. With the exception of chlorine dioxide and monochloramine, none of these alternative disinfectants provide residual disinfection in a distribution system or container and therefore typically require the supplemental use of some form of chlorine.
To be a truly effective and robust disinfectant for potable water and many similar applications, it is necessary for the disinfectant/sanitizer to be effective on both bacteria and viruses.
Alternatives to chlorine, such as ions, permanganate, chloramines and ozone/peroxide typically fail to achieve more than a 2-log inactivation of viruses. In some cases these alternative disinfectants provide no measurable inactivation of viruses, particularly in high turbidity, high organic content waters. The use of iodine is recommended by the CDC only for short-term emergency use and has significant adverse taste and aesthetic drawbacks. In summary, none of the recognized alternative disinfectants consistently achieve more than a 3-log inactivation of both bacteria and viruses while also avoiding DBP formation and providing an effective disinfectant residual that can provide microbiologically safe water during extended periods of water storage and/or after the re-inoculation of microorganisms which typically occurs when the stored water is actually used.
In addition to PWSs, there are numerous additional applications for a new, effective, safe method of water disinfection. These include water dispensers in offices and public buildings where there is concern over the microbiological quality of the water, portable water treatment for outdoor activities such as hiking and camping, use in recreational vehicles, seasonal camps and campgrounds, point of use (POU) devices such as softeners and carbon filters, counter top water treatment devices, fruit and vegetable rinses, meat, fish and poultry rinses, storage and transport ice for commercial fishing operations, military uses such as remote field use and for bulk water storage or treatment at military bases, as well as application to ships, airplanes, and the U.S. National Aeronautics and Space Administration (NASA), etc.
Treatment of non-potable water to make it safe to drink from a microbiological perspective for residential use typically involves treatment technologies such as sub-micron filtration, ultraviolet light, ozone, chlorine, iodine and/or other disinfecting chemicals. Some treatment devices make use of resins or media impregnated with biocidal compounds such as iodine so that certain levels of such biocides are released into the water. While size exclusion and ultraviolet light based systems provide essentially immediate removal or inactivation of certain microbes, they do not provide any residual disinfectant to prevent regrowth of organisms. Ultraviolet light based processes are significantly adversely affected by particulates, high organic content, turbidity and a number of chemical constituents and thus fall short of applicability to a wide range of water types. They also require some type of electrical source whether it is (alternating current) AC or (direct current) DC in nature. Size exclusion based methods are typically ineffective on removing viruses as well as some of the smaller bacteria and are impacted by limitations of throughput due to filter plugging.
The present invention represents a novel disinfection technology that utilizes a combination of metal ions and natural derivatives. It is broadly applicable to both untreated natural and/or treated municipal waters that exhibit a wide range of physical/chemical characteristics. As previously described it also is applicable to a wide range of non-drinking water applications including recreational water treatment (hot tubs, swimming pools, therapy pools), dental unit water line devices, food preparation, water re-use, industrial cooling loops, and cooling towers, etc. It can function as a stand-alone disinfection treatment or can be combined with other water treatment technologies.
While use of metal ions either alone, in combinations with other ions, or in combination with other substances such as free chlorine and hydrogen peroxide, has met with some success in bacterial inactivation in certain water types, no combination reported in the scientific literature has proven consistently effective on inactivation of viruses on a wide range of test waters even after extended contact times incorporating hours or even days. This is particularly true when trying to produce microbiologically safe drinking water based on efficacy goals and standards as established by the EPA's Surface Water Treatment Rule (SWTR) and/or in their Guide Standard and Protocol for Testing Microbiological Water Purifiers and using short contact times. Similarly, despite lay claims to the contrary, after extensive testing, citrus extracts such as the type of plant extract used within the most preferred embodiment of the present invention, when used alone, have shown an inability to achieve effective viral reduction even under clean water test conditions such as treated municipal water or untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells without protracted contact times. Laboratory testing has confirmed the inability of ions alone or plant extracts alone or the combination of ions and glycerin to achieve effective viral reduction. This same testing has consistently documented the ability of the present invention to achieve viral inactivation under identical and more rigorous test conditions. Laboratory testing using various waters seeded with bacteria and/or viruses using ions alone, plant extracts alone or a combination of ions and an alcohol (glycerin) yielded the following results:
Copper/Silver Ions Alone—Use of silver ions or specific ratios of combined copper and silver ions (10:1 to 30:1) alone resulted in 5 log and 6 log reductions, respectively, on Klebsiella after a 60 minute contact time on the seeded municipal water matrix. Copper ions alone were not as effective and yielded reductions of less than 3 log and 5 log after 60 and 240 minutes of contact time, respectively, on seeded municipal water. Copper/silver ion treatment was less effective on Pseudomonas aeruginosa in seeded municipal water than on Klebsiella with a maximum reduction of less than 5 log being achieved after a 90-minute contact time.
Use of silver or copper ions alone on untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells water seeded with Klebsiella resulted in log reductions of less than 3-log after 120 minutes of contact time. Use of combined silver and copper ions resulted in log reductions of less than 4-log after 120 minutes of contact time.
No combination of copper/silver ions alone proved even marginally effective on MS2 virus insofar as testing was directed at observing log reductions with minimal contact times, e.g. well less than 24 hours. No reduction in MS2 virus was observed after a contact time of 6 hours and less than 3-log of virus reduction was seen at 24 hours. Similar or even significantly lower inactivation results were achieved on seeded untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells with less than 1 log inactivation resulting from the use of copper or copper/silver ions after 4 hours of contact time. No effective reduction of MS2 was achieved using silver ions alone even after contact times of up to 24 hours on seeded municipal water or untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells. Therefore, use of copper and/or silver ions alone was judged to be unsatisfactory for disinfection of viruses.
In summary, ions alone, whether used individually or in combination, do not provide acceptable disinfection of municipal or untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells for both bacteria and viruses.
Plant Extract i.e. Citricidal.™ Alone—The use of Citricidal.™ alone, whether dissolved in a water or glycerin base, yielded inconsistent performances on waters seeded with Klebsiella. Log reductions on seeded municipal water ranged from 4 log to 6 log after 60 minutes. Log reductions of less than 3 log were seen on seeded untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells even after 120 minutes or longer of contact. Citricidal.™ was typically completely ineffective on MS2 virus, with no reductions being observed on seeded municipal water or seeded untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells even after 24 hours of contact.
In summary, plant extract (i.e. Citricidal.™ alone), does not provide acceptable disinfection of municipal or untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells for both bacteria and viruses.
Metal Ions and Glycerin (alcohol) Combined—The use of copper and silver ions in conjunction with glycerin yielded inconsistent performances on water seeded with Klebsiella. Log reductions on seeded municipal water ranged from 5 log to 6 log after 60 minutes. Log reductions on heterotrophic bacteria on unseeded untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells was less than 1.5 log. No reductions of MS2 virus were observed on seeded municipal or untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells using a combination of ions and glycerin.
In summary, a combination of ions and glycerin does not provide acceptable disinfection of municipal or untreated natural waters such as water from rivers, streams, brooks, ponds, lakes, springs or wells for both bacteria and viruses.
As previously stated, the present invention represents a unique combination of metal ions together with natural plant extracts and alcohols. As such, it is a new and novel technique and has not previously been reported in the literature or prior art patents. A number of researchers have previously attempted to find suitable alternatives to chlorine disinfection, each of which have well-documented drawbacks. Investigators have tried to take advantage of the antimicrobial properties of copper and silver ions and to optimize their effect, particularly against viruses, by combining them with various other ingredients. However, previous efforts have failed to develop any copper/silver combination disinfectants that have been demonstrated to achieve acceptable inactivation of both bacteria and viruses within short contact times. Some relevant research is briefly reviewed below.
Domek, et al., as disclosed in Domek, M., M. LeChevallier, S. Cameron and G. McFeters, 1984, Evidence for the Role of Copper in the Injury Process of Coliform Bacteria in Drinking Water, Appl. Environ. Microbiol. 48: 289-293, demonstrated that the presence of low levels of copper causes damage to E. coli in drinking water samples, and that the effect was dose dependent. Subsequent testing indicated reduced oxygen uptake and glucose utilization by copper-injured cells, as well as changes in metabolic end products.
Kutz, et al., as disclosed in Kutz, S., L. Landeen, M. Yahya and C. Gerba. 1988, Microbiological Evaluation of Copper: Silver Disinfection Units, Proceedings of the Fourth Conference on Progress in Clinical Disinfection, S.U.N.Y., Binghamton, N.Y., Apr. 11-13, 1988, examined electrolytically generated copper (Cu) and silver (Ag) ions alone, free chlorine (FC) alone and Cu/Ag ions plus low levels of FC against seven types of bacteria. Their results indicated that all the bacteria tested were inactivated more rapidly with the combined treatment than by either treatment individually.
Landeen, et al., as disclosed in Landeen, L., M. Yahya, and C. Gerba 1989, Efficacy of Copper/Silver Ions & Reduced Levels of Free Chlorine in Inactivation of Legionella pneumophila, Appl. Environ. Microbiol. 55: 3045-3050, also tested copper and silver ions with and without FC, using Legionella as the challenge organism, and reported statistically significant improvement in disinfection from the combined treatment.
Yahya, et al., as disclosed in Yahya, M., L. Landeen, M. Mesina, S. Kutz, R. Schultze and C. Gerba, Disinfection of Bacteria in water Systems by Using Electrolytically Generated Copper: Silver & Reduced Levels of Free Chlorine, Can. J. Microbiol. 36: 109-116, conducted similar testing using Staphylococcus sp., which previous research had indicated might be more resistant to treatment than coliform bacteria, and reached similar conclusions regarding the benefit of adding FC to the treatment and the limitations of copper/silver ions alone.
Margolin, et al., as disclosed in Margolin, A. B. Control of Microorganisms in Source Water and Drinking Water. pp. 274-284, In: Manual of Environmental Microbiology, Hurst, C. J., Ed., ASM Press, Washington D.C., 2002, evaluated inactivation of MS2 and poliovirus by leached copper with and without added FC. They reported poliovirus showed more resistance to disinfection by copper than MS2 (1.3 log and 4.0 log inactivation in 12 hours, respectively) and that the addition of FC significantly enhanced the inactivation of both viral types.
Abad, et al., as disclosed in Abad, F., R. Pinto, J. Diez and A. Bosch, 1994, Disinfection of Human Enteric Viruses in Water by Copped Silver in Combination with Low Levels of Chlorine, Appl. Environ. Microbiol. 60(7):2377-2383, tested the efficacy of copper and silver ions in combination with low levels of FC against enteric viruses. They reported that copper plus silver plus 0.5 mg/L FC was no more effective against poliovirus than 1 mg/L FC alone. The authors also observed that under the test conditions, adenovirus required 120 minutes of disinfectant contact to achieve 3 log reduction, and Hepatitis A Virus (HAV) and human rotavirus were even more resistant. The authors concluded that (as applied) copper and silver in water may not provide a reliable alternative to high levels of FC for disinfection of viral pathogens. However, they also reported the stability of copper and silver levels in the test chambers, with 75% and 44% of the initial inputs, respectively, detectable after 60 days.
Lin, et. al., as disclosed in Lin, Y., R. Vidic, J. Stout and V. Lu, 1996, Individual and Combined Effects of Copper and Silver Ions on Inactivation of Legionella Pneumophila, Wat. Res. 30(8): 1905-1913, examined the efficacy of copper and silver ions, alone and in combination, against L. pneumophila serogroup 1. These authors noted that copper was more effective than silver alone, but required a contact time of 2.5 hours to achieve complete (6 log) inactivation of Legionella (silver required 24 hours).
Significantly, Lin, et al. also noted that copper and silver ions could result in either additive or synergistic effect, depending upon the concentrations used, and concluded that their combined effect is greater than that observed from either copper or silver alone.
Rohr, et al., as disclosed in Rohr, U., S. Weber, F. Selenka and M. Wilhelm, 2000, Impact of Silver and Copper on the Survival of Amoebae and Ciliated Protozoa in Vitro, Int. J. Hyg. Environ. Health 203: 87-89, examined the effect of copper and silver ions against amoebae and ciliated protozoa in vitro. The authors reported that within the German drinking water regulatory limits (10 and 100 mg/L for Ag and Cu, respectively), the combined treatment did not inactivate the test protozoa.
Batterman, et al., as disclosed in Batterman, S., K. Mancy, S. Wang, L. Zhang, J. Warila, O., Lev, H. Shuval and B. Fattal, 2001, Evaluation of the Efficacy of a New Secondary Disinfectant Formulation Using Hydrogen Peroxide and Silver and the Formulation of Disinfection By-products Resulting From Interactions With Convention Disinfectants, EPA STAR Grant No. R825362, working under an EPA STAR grant, evaluated the efficacy of combined treatment of hydrogen peroxide (H.sub.2O.sub.2) plus copper and silver ions. For bacteria, they reported that the hydrogen peroxide was less effective than silver ions, which was less effective than the combination of H.sub.2O.sub.2 and silver ions, which was less effective than H.sub.2O.sub.2 plus copper ions. However, the authors concluded that the combined disinfectant achieved unacceptable viral inactivation. Six (6) hours of contact time was required to inactivate 4 logs of MS2 coliphage and the efficacy against poliovirus was even worse, achieving only 0.15 log inactivation after 12 hours of contact time.
As can be seen from the above cited research, while the use of copper and silver ions, either alone or in combination with other substances, has met with success on bacterial inactivation, no combination has proven effective within short contact times on viruses on a wide range of test waters.
Similarly the prior art patents disclose a number of examples of antimicrobial agents that have incorporated metal ions either alone or with other substances. The prior art patents, however, typically teach disinfection systems for non-potable water uses such as swimming pools and spas. In a few instances the prior art patents include treatment systems intended for potable water. None of these prior art patents teach the use of combining EPA potable concentrations of plant extracts, alcohols and metal ions for the disinfection of water of bacteria, algae, protozoans, virus and fingi in water that has an effective kill rate that renders a previously contaminated water source potable in a matter of minutes or hours and that provides disinfectant residual that remains effective for killing or inactivating bacteria and viruses for months or years while not forming disinfection byproducts.